In the development of athletic floor systems, particularly hardwood floor systems, it is desirable to reduce the occurrence of injuries caused by the floor and to provide a surface with highly consistent performance characteristics during competition. While certain gains have been made toward these ends, further improvements are still desirable. In order to measure the ability of a floor system to meet the desired characteristics of reduced injury and consistent performance, the Otto Graf Institut of Stuttgart, West Germany has established a set of standards or requirements for hardwood floor systems.
Hardwood floor systems have been generally preferred over other playing surfaces because wood wears slowly and uniformly, provides long functional service, possesses natural warmth, beauty and resilience characteristics with only modest maintenance costs. A typical hardwood floor system is laid on a base such as a concrete or asphalt slab, or a pre-existing floor. An intermediate support means or layer is secured to the base. A top layer of hardwood maple floorboards is secured to the support surface and forms the actual playing surface. Another type of athletic flooring system which is not secured to the base, is referred to as a free-floating floor. In such a floor, the top hardwood floor board layer and intermediate layer float freely with respect to the base. A layer of filler made of a foam or cushion material may reside between the base and the intermediate support layer and/or between the top layer and the intermediate layer.
The supporting layer or layers residing beneath the maple floorboards maintain the relative positions of the floorboards in a set position, withstanding movement due to moisture changes in the wood, or flexing action of the floor. In order to reduce the occurrence of injury during use of the floor, the supporting layer must also provide a desired degree of shock and resiliency, or give, so that upon impact, the floor system will reduce the amount of force that is imparted by the floor system upon the impacting object.
In order to reduce this force, a hardwood floor system must deflect downwardly and absorb a degree of energy upon impact. Moreover, as the amount of downward deflection built into the floor system increases or as the stopping distance of the impacting object increases, the amount of force that can be absorbed also increases. Thus, for a hardwood athletic floor system, in order to reduce the likelihood of athletic injury resulting from impact with the floor, it is desirable to increase the vertical deflectability of the floor surface.
At the same time, while downward deflectability is desirable, hardwood athletic floors must also possess certain qualities which, by their nature, restrain or limit the amount of deflectability that is attainable. For instance, a hardwood floor system must have some degree of firmness, in order to provide at least a minimum accepted level of ball reflection and foot stability. Otherwise, for sports such as basketball, the entire complexion of the game would be drastically changed.
Moreover, a hardwood floor must also provide uniform response characteristics, regardless of the timing or location of an impacting object. In other words, the amount of surface area that is deflected upon impact should be minimal, so that deflection caused by one impacting object only minimally affects the floor's response to a nearby impacting object. Again, this is especially true for sports such as basketball, where the competitors are often quite close, and the floor undergoes numerous impacting forces within a relatively small surface area.
Thus, an inevitable problem arises, that of designing a hardwood floor system that provides significant deflection and shock absorption upon impact, in order to reduce injury, yet at the time confines, or attenuates the total surface area of deflection. Recognition of this problem is confirmed through standards established by the Otto Graf Institut, of Stuttgart, West Germany, in a series of test procedures which measure the critical performance characteristics of hardwood floor systems. The measured characteristics are: shock absorption; vertical deflection at impact; attenuation of vertical deflection within a given surface area; ball reflection; sliding characteristics and rolling load behavior, and the test is identified as DIN #8032 part 2 (hereinafter referred to as "the DIN test"). To a large degree, the DIN test provides an indication of whether or not a particular floor system achieves an adequate solution for the above noted problems.
Several prior art patents disclose so-called shock absorbent floors. For example, Fritz U.S. Pat. No 2,919,476 discloses a floor system designed to maximize the total surface area of deflection upon impact. However, a floor system of this type also causes unwanted deflection or "springiness" in areas that are adjacent to the point of impact. It would appear that Fritz would, upon impact, create huge dead spots or areas which cannot fully react to a second adjacent impact. As stated previously, for a sport such as basketball, the deflection caused by one player may adversely affect the play of another. Thus, the Fritz teaching to maximize the surface area of deflection upon impact runs counter to the acknowledged desire to attenuate impact deflection within a minimum surface area.
Stephenson U.S. Pat. No. 4,682,459 discloses a floor system having three layers of 4'.times.8' subflooring panels with the seams of the layers aligned in a specified pattern. The use of three subflooring layers to support the floorboards, along with spaced pads and an intermediate layer of cushion, is considered excessive, and results in an increase in the overall cost of material and installation for the floor system.
Despite these and other efforts, no known maple strip hardwood floor has met all the DIN standards for shock absorption, vertical deflection at the point of impact, a prescribed attenuation of deflection within a given surface area, ball reflection, sliding characteristics and rolling load behavior.
It is accordingly an object of this invention to provide an improved hardwood floor system that meets the six above-stated requirements of the DIN test.
It is another object of this invention to provide a hardwood, free-floating floor system that meets the six above-stated requirements of the DIN test, and at the same time provides a monolithic-like support system for the floorboards.
It is still another object of this invention to provide a hardwood free-floating floor system that meets the six above-stated requirements of the DIN test, but is relatively inexpensive compared to prior free floating floor systems.